The present invention relates to an activation control apparatus of an occupant safety system for controlling activation of the occupant safety system such as an airbag system or the like for protecting occupants in a vehicle in the event of a vehicle collision.
The conventional activation control apparatus for controlling the activation of the occupant safety system is designed to detect impact on the vehicle by measuring deceleration with an acceleration sensor normally mounted on the floor tunnel, compute an operation value based on the deceleration thus detected, compare the operation value with a preset threshold, and control firing of squib, based on the result of the comparison.
Here vehicle crash types are classified under frontal crash, oblique crash, pole crash, offset crash, under-ride crash, etc., as illustrated in FIG. 14A to FIG. 14F, according to the way of collision, the direction of collision, the type of a colliding object, and so on. In the event of the frontal crash out of them, because the vehicle is designed to absorb the impact upon crash by the two left and right side members, great deceleration appears on the floor tunnel, on which the floor sensor is mounted, in a predetermined time after the crash. In contrast with it, in the event of the crash except for the frontal crash, because the way of absorbing the impact is different from such impact absorption, the deceleration is not so great on the floor tunnel in the predetermined time after the crash.
In order to detect the crash except for the frontal crash, it is, therefore, necessary to place a sensor other than the floor sensor in the front part of the vehicle so as to accurately detect the impact upon the crash except for the frontal crash.
An object of the present invention is to provide an activation control apparatus of an occupant safety system capable of activating the occupant safety system at optimum timing.
The present invention provides an activation control apparatus of an occupant safety system comprising a first sensor disposed at a predetermined position in a vehicle, for detecting impact on the vehicle, activation control means of the occupant safety system for activating the occupant safety system when an operation value obtained based on a detection value detected by the first sensor exceeds a predetermined threshold, a second sensor disposed more to the front than said first sensor in the vehicle, for detecting a level of impact on the vehicle to detect values of at least two different magnitudes according to the level of the impact detected, and threshold changing means for changing the predetermined threshold according to a detection value of the second sensor, wherein the threshold changing means comprises threshold change amount increasing means for increasing a change amount of the predetermined threshold with increase in a value based on the detection value of the second sensor.
The present invention is also characterized in that the value based on the detection value of the second sensor is a value resulting from integration of the detection value of the second sensor over a predetermined duration.
The present invention is also characterized in that the threshold change amount increasing means is arranged to subtract a value based on an operation value resulting from the integration of the detection value of the second sensor over a predetermined duration, from the predetermined threshold.
The present invention is also characterized in that the operation value obtained based on the detection value of the first sensor is a value resulting from the integration of the detection value of the first sensor over a predetermined duration.
The present invention is also characterized in that the second sensor is comprised of two sensors and the greater out of detection values detected by the two sensors is defined as the detection value of the second sensor.
The present invention is also characterized in that the second sensor is located in a front center part of the vehicle.
The present invention is also characterized in that the second sensor is arranged to detect levels of the impact on the vehicle and output detection values thereof as linear values.
The present invention is also characterized in that the second sensor is a mechanical sensor which detects levels of the impact on the vehicle and which outputs detection values thereof as values of two different kinds.
According to the present invention, the threshold changing means changes the predetermined threshold used for activation judgment of the occupant safety system in accordance with the detection value of the second sensor and the threshold change amount increasing means increases the change amount of the predetermined threshold used for the activation judgment of the occupant safety system with increase in the detection value of the second sensor; therefore, the occupant safety system can be activated at optimum timing.
The present invention is also characterized in that the threshold changing means comprises threshold change amount decreasing means for decreasing the change amount of the predetermined threshold corresponding to an initial increase state of the operation value based on the detection value of the first sensor.
According to the present invention, the threshold change amount decreasing means decreases the change amount of the predetermined threshold corresponding to the initial increase state of the operation value based on the detection value of the first sensor; therefore, the occupant safety system can be prevented from undergoing oversensitive activation due to the impact etc. during vehicle running on rough roads.
The present invention is also characterized in that the threshold changing means is arranged not to change the predetermined threshold corresponding to the initial increase state of the operation value based on the detection value of the first sensor when the operation value based on the detection value of the second sensor exceeds a predetermined value.
According to the present invention, a change start time of the predetermined threshold can be delayed, because the threshold changing means is arranged not to change the predetermined threshold corresponding to the initial increase state of the operation value based on the detection value of the first sensor when the operation value based on the detection value of the second sensor exceeds the predetermined value; therefore, the occupant safety system can be prevented from undergoing oversensitive activation due to the impact etc. during vehicle running on rough roads.
The present invention is also characterized in that the second sensor comprises a right sensor and a left sensor placed right and left in the front part of the vehicle and the threshold changing means changes the predetermined threshold in accordance with magnitude of a difference between impacts detected by the right sensor and by the left sensor.
According to the present invention, the threshold changing means changes the predetermined threshold used for the activation judgment of the occupant safety system in accordance with the magnitude of the difference between the impacts detected by the right sensor and by the left sensor. Since the magnitude of the difference between the impacts detected by the right sensor and by the left sensor differs depending upon the crash part of the vehicle, the optimum activation control of the occupant safety system can be carried out according to the crash part of the vehicle by changing the predetermined threshold in accordance with the magnitude of the difference between the impacts detected by the right sensor and by the left sensor.
The present invention is also characterized in that the second sensor comprises a right sensor and a left sensor placed right and left in the front part of the vehicle and the threshold changing means changes the predetermined threshold in accordance with magnitude of a difference between the impacts detected by the right sensor and by the left sensor or a ratio of the impacts detected by the right sensor and by the left sensor.
According to the present invention, the optimum activation control of the occupant safety system can be carried out according to the crash part of the vehicle, because the threshold changing means changes the predetermined threshold in accordance with the magnitude of the difference between the impacts detected by the right sensor and by the left sensor or the ratio of the impacts detected by the right sensor and by the left sensor.